1. Field of the Invention
The present invention is in the field of pressure accumulator devices and is directed more particularly to a device of the type described wherein little or no sound is generated by the seating and unseating of the valve member.
2. The Prior Art
Hydraulic accumulator devices (such description to include pulsation dampeners) commonly include a pressure vessel or shell having a gas charging port at one end and an oil port at the other end. An elastomeric bladder member divides the vessel into two chambers communicated, respectively, with the gas and oil ports.
The oil port is connected to a source of hydraulic fluid or the like which is subjected to intermittent periods of high and low pressure. The gas chamber is charged with a quantity of gas under pressure. When the pressure in the gas chamber sufficiently exceeds pressure in the oil chamber, the bladder is distended to the point where the bladder seals the oil port. By virtue of the readily ruptured nature of the material of which the bladder is made, some form of protection is desirably afforded to those portions of the bladder which contact the oil port, to prevent the bladder from being extruded therethrough.
Heretofore it has been proposed to form the bladder with a thickened tip portion in the area in registry with the oil port, whereby, upon expansion of the bladder, the thickened and hence tougher portion of the bladder will contact the port. A representative example of a pressure vessel employing such construction is embodied in U.S. Pat. No. 3,433,268 wherein an elastomeric bladder includes a sealing portion, said portion being rigidified by a metallic stiffener molded into the end of the bladder. It will be readily recognized that bladders of the type described are expensive to manufacture and their replacement requires complete disassembly of the pressure vessel.
It has further been established that upon repetitive seatings and unseatings of the valve, the elastomeric material will ultimately be compromised, to define a leakage path across the valve, with the result that the entire bladder assembly must thereafter be replaced at substantial cost.
In a construction shown by way of example in U.S. Pat. No. 2,604,118, there is disclosed a hydraulic accumulator assembly wherein the wear problem of the valve portion is solved by the provision of a metallic valve member either bonded directly to the bladder or screw threadedly connectible to the bladder.
Both of the embodiments disclosed in said patent are disadvantageous in environments where sudden pressure drops in the hydraulic line may be experienced since the seating of the valve component is accompanied by a substantial metal-against-metal impact, with the production of a loud noise and the transmission of vibration throughout the hydraulic system.
While there is proposed in one embodiment a replacement valve member which may be threadedly connected to the bladder, the form of connector suggested in said patent involves the provision of a through-going aperture in the bladder, with a threaded member being located to one side of the aperture, the valve incorporating a complemental threaded component received in the internally threaded member, reliance being placed upon the tightening of the threaded components to seal the aperture in the bladder.
It has been discovered that such arrangement is disadvantageous in that ultimately gas leakage through the aperture of the bladder is experienced. Also, replacement of the valve member presupposes access both to the valve at one side of the bladder and the insert at the other side of the bladder, so that sufficient relative torsional forces may be developed clampingly to seal the aperture of the bladder.